Mixed Berry Muffins with Crumble Topping

Name: Mixed Berry Muffins with Crumble Topping
Prep time: 10 min
Total time: 10 min
Cuisine: American
Ingredients: 2 tablespoons melted butter; ¼ cup old-fashioned rolled oats; ¼ cup flour*; 3 tablespoons brown sugar; 1 teaspoon ground cinnamon; 2 cups flour*; 1 ½ teaspoons baking powder; 1 teaspoon baking soda; ½ teaspoon coarse salt; ⅓ cup oil; ½ cup brown sugar; 2 large eggs; 1 ½ teaspoons vanilla extract; ⅓ cup milk; 1 ½ cups mixed berries (fresh or frozen)